Multi-site communication systems provide wide-area coverage for users of the system. These systems comprise a number of sites, with each site corresponding to a different geographic coverage area and each site having located therein an infrastructure device (which will hereinafter be referred to as a repeater) serving the coverage area by managing one or more channels in the coverage area. Accordingly, for purposes of the teachings herein, a site is characterized by a repeater that serves a particular coverage area, a channel for wireless communication device transmissions, and a system identification that identifies transmissions from the repeater on the channel at the site. Some or all of the infrastructure devices in a multi-site communication system may be networked or connected together via a backend network to provide the wide-area coverage via one or more logical wide-area channels, and in many instances two or more of the coverage areas have some degree of overlap.
Multi-site communication systems may be designed as trunked systems or conventional systems. In trunked systems, a limited number of communication channels are shared among a much larger number of users to facilitate efficient use of the system's communication resources. Thus, to afford each user a reasonable opportunity to use the system's resources, one or more control channels are utilized by the infrastructure to allocate the shared resources between the many users in the system. In general, when a wireless communication device (which will hereinafter be referred to as a radio) wants to communicate on the trunked system, it sends a request on the control channel to communicate with another radio or group of radios. In turn, the requesting radio (and the radios to which it desires to communicate) receives back on the control channel the allocation of a traffic channel to use for their communications. Upon the conclusion of the communications, the allocated channel is released for use by other radios in the system.
In conventional systems, a number of communication channels are also shared amongst a number of users (although the number of users per channel is typically much smaller than in trunked systems). However, there is no control mechanism provisioned in the infrastructure to allocate the resources among the users in the system. Thus, in contrast to a trunked system, each channel in a conventional system is dedicated to one or more groups of users enabling the users to control access to the channels through their radios by manually selecting a channel or selecting a talkgroup that is assigned a particular channel in order to start a communication session and transmit and receive media during the session.
In a conventional multi-site communication system where the repeaters are networked or coupled together, one of the repeaters may receive a transmission indicating a start of a first session and begin repeating the transmissions of that first session. The repeater will also notify other repeaters in the system to repeat the transmissions of the first session. However, due to timing lags in the backend network that connects the repeaters, one or more of the other repeaters may start repeating transmissions for a different session prior to receiving the notification for the first session. This is undesirable because for proper operation of the system, all of the repeaters should be repeating the transmissions of the same session so that all participants to the session can transmit and receive media during the session without interruption regardless of their location within the multi-site communication system.
It is known for the repeaters in a multi-site communication system to use an arbitration process, wherein the repeaters coordinate among each other which session will be provided access to a wide-area channel so that each repeater repeats transmissions for the same session and denies access to the wide-area channel for transmissions for a different session. However, a shortcoming is that the arbitration process is performed each time before repeating a transmission, which causes undesirable time delays in ongoing communications within the system.
Thus, there exists a need for a method for controlling access to a channel in a conventional multi-site communication system, which does not require a repeater to perform an arbitration before each repeated transmission.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. Apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.